A generic micro pump operates according to the principle of a gear pump. It comprises an inner rotor with external teeth and an outer rotor with internal teeth. The external teeth of the inner rotor are in meshing engagement with the internal teeth of the outer rotor. The two axes of inner rotor and outer rotor are offset with respect to each other by an eccentricity. Due to this offset of axes, the two rotors engaged with each other define a pump chamber or a plurality of pump chambers therebetween, which cyclically change(s) in size and position due to rotation of the rotors.
Such a micro pump is known, for example, from WO00/17523 A1. An inner rotor and outer rotor are formed and arranged in an intermeshing manner, wherein both the inner rotor and the outer rotor are rotatably arranged in a sleeve. The inner rotor is coupled to a shaft in a torque proof manner. The axis of the outer rotor is offset with respect to the axis of this shaft so that the inner rotor with its outward oriented teeth eccentrically rolls on the inward oriented tooth structure of the outer rotor and axial sealing lines are formed depending on the number of teeth, wherein respective pairs of sealing lines define a delivery chamber. These delivery chambers expand in a direction of rotation on the suction side, take up fluid there and deliver it across a virtual center plane extending through the axis to the pressure side, where the delivery chamber having just passed across continuously decreases in the course of the further rotation until it becomes virtually zero and is returned to the suction side on the opposite side of the center plane. Here, the said pump chamber begins to open again continuously with the rotational movement so that the cycle is completed. The movement described with respect to a delivery chamber simultaneously applies to all existing delivery chambers having a different volume between a respective pair of sealing lines at a current time so that a highly uniform delivery flow results during operation of the pump providing a high capability of miniaturization of the entire micro-system structure.
Generic pumps and micro pumps, especially of the type described above, are accommodated in a housing protecting the pump and sealing it from the environment. A possible housing shape for accommodating such a micro pump is known from a data sheet “Pumpenkopf (pump head) Mzr® 4600” of HNP Mikrosysteme GmbH. This pump head comprises a shaft protruding from the face for coupling a motor thereto. Five disk-shaped elements, as cylinder elements, define a housing structure beginning with a housing shaft seal, a compensating kidney plate and a rotor accommodating plate, followed by a fluid guide and a cover. A bore is provided in the rotor accommodating plate which is eccentrically offset with respect to the axis of the shaft for driving the internal gear so that the outer rotor is mounted off-center in the rotor accommodating plate. The compensating kidney plate is located on one side of the outer rotor and inner rotor and the fluid guide plate directly abuts thereon on the face on the opposite side. Both plates comprise input and output kidneys directed towards the rotor on the side of the fluid supply and compensating kidneys arranged in mirror-image fashion for creating a hydraulic balance on the opposite side. Thus, a U-shaped fluid flow arises from the inlet via the inlet kidney to the rotating pump chambers towards the outlet and back to the outlet, which is guided out radially in data sheet Mzr® 4600.
DE B 33 10 593 (White) shows a housing structure for a pump arrangement realizing, along with a wobble rod, an eccentrically operating gerotor. An outlet is provided centrally at the end not penetrated by the shaft and an inlet is provided radially offset thereto, wherein a plurality of intermediate plates comprising channel segments are provided therebetween. DE A 24 08 824 (McDermott) operates with only three plate-shaped structures and shows the gerotor principle in connection with a compensation of signs of wear of the intermeshing teeth, wherein channel segments are provided in the directly adjacent region between an inner disk and the two outer bearing disks for the shaft. CH A 661 323 (Weber) is also concerned with channel segments in a housing structure composed of a plurality of disks, which structure forms a gear pump in the manner of a kit made up of a plurality of component parts which are easy to assemble, to replace and to be supplemented, while actually describing a housing for accommodating such a pump.
It is disadvantageous in known prior art pumps having a housing that they comprise a great number of individual component parts, especially component parts which need to be manufactured with high precision for reliable operation of the pump. Manufacture must be carried out with very narrow tolerances so that accommodation of the rotors in the housing, which is ultimately determined by the numerous individual component parts, can be effected with sufficient tightness while simultaneously ensuring good mounting. Furthermore, each component part attached to another individual component part must be sufficiently sealed, especially when in contact with moving elements of the pump or penetrated thereby. Shaft seals must be dynamic which results in increased maintenance effort and costs. Assembly is complicated by the great number of parts.